Acetic Acid-Catalyzed Regioselective C(sp2)-H Bond Functionalization of Indolizines: Concomitant Involvement of Synthetic and Theoretical Studies

Thermodynamic Controlled Regioselective C1-Functionalization of Indolizines with 3-Hydroxyisoindolinones via Brønsted Acid Catalyzed aza-Friedel-Crafts Reaction

A Brønsted acid catalyzed aza-Friedel-Crafts reaction of indolizines with 3-hydroxyisoindolinones has been established, which constructs isoindolinone derivatives bearing a tetrasubstituted stereocenter in good to high yields and enantioselectivities. Notably, this strategy provides a new access to C1-functionalization of indolizines with excellent regioselectivities. Moreover, this intriguing C1-regioselective transformation was induced under thermodynamic control.

Switchable Synthesis of Spirodihydroindolizines and Indolizines from Aurones and Pyridin-2-yl Active Methylene Compounds

A novel and flexible domino reaction of aurones with pyridin-2-yl active methylene compounds promoted by I2/BF3 has been developed to afford spirodihydroindolizines and indolizines in a controllable manner. When the reaction was performed in 1,2-dichloroethane at 80 °C, a variety of spirodihydroindolizines were obtained, whereas it almost exclusively provided a series of indolizines when the reaction was performed in a mixed solvent of 1,2-dichloroethane and N,N-dimethylformamide at a relatively higher temperature of 100 °C. Being metal-free, excellent product selectivity, high atom economy, good functional group tolerance, and feasibility for large-scale synthesis are the salient features of the developed methodology.

Gold-Catalyzed Alkyne Multifunctionalization through an Oxidation-Oxyalkylation-Aryloxylation Sequence

A gold-catalyzed oxidative three-component reaction of terminal alkynes with alcohols and quinone monoimines has been disclosed, affording α-ketoacetals in good to excellent yields. By using quinone monoimines as electrophiles for the interception of the in situ generated gold enolate intermediate, this one-pot process provides an unprecedented method for the polyfunctionalization of terminal alkynes through an oxidation-oxyalkylation-aryloxylation sequence, installing three oxygen atoms on the C-C triple bond.

Catalytic Atroposelective Electrophilic Amination of Indoles

Reported here is the first catalytic atroposelective electrophilic amination of indoles, which delivers functionalized atropochiral N-sulfonyl-3-arylaminoindoles with excellent optical purity. This reaction was furnished by 1,6-nucleophilic addition to p-quinone diimines. Control experiments suggest an ionic mechanism that differs from the radical addition pathway commonly proposed for 1,6-addition to quinones. The origin of 1,6-addition selectivity was investigated through computational studies. Preliminary studies show that the obtained 3-aminoindoles atropisomers exhibit anticancer activities. This method is valuable with respect to enlarging the toolbox for atropochiral amine derivatives.